Kotlin basic syntax

Hello.kt

import java.util.*

fun main(args: Array<String>) {
    println("Hello, world")
    basicTypes()

    val c = cls("Accessible", "Unsettable")
    c.publicMethod()
    c.accessible = "Accessible value is updated !"
    // c.unsettable = "ERROR!!!"
    println(c.accessible)
    println(c.unsettable)
    println("--------------------")
    c.publicMethod()
}

/**
 * クラスでGetter/Setterの定義をする.
 * varだとGetter/Setterともに定義されるが、
 * valだとGetterのみ定義される.
 */
class cls(var accessible: String, val unsettable: String) {
    val publicValue = "Public"
    private val privateValue = "Private"

    init {
        // コンストラクタチックな処理はここで行う
    }

    fun publicMethod() {
        println("public")
        println(accessible)
        println(unsettable)
        println(publicValue)
        println(privateValue)
        privateMethod()
    }

    private fun privateMethod() {
        println("private")
        println(accessible)
        println(unsettable)
        println(publicValue)
        println(privateValue)
    }
}

fun basicTypes() {
    // 変数宣言
    var foo: String = "Hoge"
    foo = "Fuga"
    // 定数宣言
    val bar: Int = 0
    // bar = 1  // Error

    // 型推論
    val integer = 0         // Int
    val dbl = 0.0           // Double
    println(integer is Int) // true
    println(dbl is Double)  // true
    // println(int is Double) // Error

    // 基本型たち
    //// 数値系
    val byte: Byte = 0x1
    val short: Short = 2
    val int: Int = 3
    val long: Long = 4L
    val float: Float = .5f
    val double: Double = 9.99
    //// 文字系
    val chr: Char = 'c'
    val str: String = "string"
    //// 論理系
    val bool: Boolean = true
    //// 配列
    val array: Array<String> = Array(3, { "0" })    // "0", "0", "0"
    val intArray: IntArray = intArrayOf(1, 2, 3)    // 1, 2, 3

    // ヒアドキュメント
    val hearDoc = """
    for (c in "foo")
        print(c)
    """
    println(hearDoc)

    // 文字列テンプレート
    val tmpl = "float is $float"
    println(tmpl)   // float in 0.5
    println("str length is \"${str.length}\"")  // str length is 6
    val price = """
    ${'$'}$double
    """ // $を文字として使いたい場合、上記のようなエスケープが必要. \によるエスケープは無いとのこと
    println(price)  // $9.99

    // Nullable
    var nullable: String? = null
    println(nullable)   // null
    println(nullable?.length)   // null
    nullable = "hoge"
    println(nullable)   // hoge
    println(nullable?.length)   // 4
    println(nullable!!.length)  // 4
    nullable = null
    println(if (nullable != null) nullable.length else -1 ) // -1
    println(nullable?.length ?: -1) // ↑と同じ(エルビス演算子)
    // println(nullable!!.length)   // NullPointerExceptionがthrowされる
}

fun returnValue(x: Int, y: Int): Int {
    return x + y
}

fun simpleReturnValue(x: Int, y: Int) = x + y

fun noReturn() {
}

fun noReturn2(): Unit {
}

fun exampleFor() {
    val array = Array(5, { i -> i })
    for (i in 0..array.size - 1) print("$i, ")    // 0, 1, 2, 3, 4,
}

fun exampleWhile() {
    val array = Array(5, { i -> i })
    var i = 0;
    while (i < array.size) print("${array[i++]}, ")  // 0, 1, 2, 3, 4,
}

fun conditionalOperation(x: Int, y: Int) {
    if (x > y) {
        println("$x > $y")
    } else {
        println("$x <= $y")
    }

    if (x > y) println("$x > $y")
    else println("$x < $y")
}

fun shortConditionalOperation(x: Int, y: Int) = if (x > y) x else y

fun whenExp(v: Any) {
    when (v) {
        is Int -> println("Int")
        is String -> println("String")
        else -> println("else")
    }
}

fun usefulWhen(x: Int) {
    when (x) {
        in 0..9 -> println("$x is small")
        in 10..20 -> println("$x is big")
        else -> println("I can't count $x !")
    }
}

fun checkRange(x: Int) {
    println(x in 0..10)
    println(x !in 4..6)
    val y = 10
    println(x in 0..y - 1)
}